It is reported that on the first night of Ramaḍān, ‘Umar – Allāh be pleased with him – would pray Maghrib, then say (to the people):

Sit down. Then he would give a small address: Verily the fasting of this month has been made a duty upon you, and standing in night prayer has not been made a duty upon you, but those amongst you who can stand in prayer should do so, for it is from the extra good deeds about which Allāh told us: so whoever cannot stand in prayer, let him sleep on his bed.

And beware of saying: I will fast if so and so fasts and I will stand in night prayer if so and so stands in prayer. Whoever fasts or stands in night prayer, he must make this for Allāh. And you should know that you are in prayer as long as you are waiting for a prayer.

Minimize any vain or false speech in the houses of Allāh (mosques; he said this two or three times). Let none of you fast a few days before the month (in order to avoid missing the beginning of the month; he said this three times). And do not fast until you see [the crescent of the new month] unless it is overcast. If it is overcast, count [the previous month] as 30 days. Then do not break your fasts until you see the night upon the mountain (i.e. you are sure the sun has set).

It is related from some of the Salaf that backbiting, tale carrying and the likes break the fast, and it is mentioned as one opinion in the madhab of Imām Aḥmad. The final word on this issue is that Allāh the Exalted commanded people to fast in order to achieve piety (taqwā), and Allāh’s Messenger – praise and peace of Allāh be upon him – stated:

Whoever does not leave off false speech and acting by it; then Allāh is not in need of him abandoning his food and drink.

So if the fasting person does not achieve piety, he has not achieved what is intended through fasting, and so the reward of [his] fast will decrease in accordance [with how much he has gone against the intended goal, i.e. commensurate with his sins].

Righteous deeds have two intended goals: gaining reward and avoiding punishment. If a person fasts while also doing forbidden things, like backbiting, carrying tales between people or consuming what is forbidden and so on, he loses the reward.

Thus, when the imams say [backbiting etc.] does not break the fast, it means that the person who sins is not punished in the way a person who openly breaks his fast would be punished.

And those who said it does break the fast in the sense that the person has not achieved the intended goal behind fasting, or in the sense that he has lost the reward for fasting, then this statement is in agreement with the position of the imams.

One who says it breaks the fast in the sense that the person is to be punished for leaving [the fast], then he is in contradiction to the imams.

Conclusion

A person who disobeys Allāh while fasting hasn’t truly grasped the intent behind fasting. The real goal is to achieve piety and obedience of Allāh through the abandonment of food, drink and sin. Although a person who backbites, lies or does other sins is not considered to have physically broken his fast, he loses the reward of fasting and in this sense he has broken his fast.

ʿAbdullāh b. Al-Ḥasan used to often sit with Rabīʿah. One day they were revising and studying various practices from the Sunnah when a man in the gathering said, “[But] this is not what is practiced [by the people].” ʿAbdullah said, “So if the ignorant become so numerous that they become the rulers and judges, will they then be a proof over the Sunnah?” Rabīʿah said, “I bear witness that these are the words of the sons of the Prophets.”

Abū ‘Ubaydah b. Al-Jarrāḥ – Allāh be pleased with him – said, when asked about making up missed fasts of Ramaḍān separately, “Allāh did not legislate upon you the breaking of the fast, and then cause hardship on you when making it up, so count the days [you excusably missed] and fast them as you wish.”

Ibn Abī Shaybah, op. cit. article 9133.

Anas b. Mālik – Allāh be pleased with him – said, “If you wish, make up [missed fasts of] Ramaḍān consecutively, or if you wish, make them up separately.”